Under existing 1968 legislation aimed at measurement of blood alcohol, drivers who were under the concurrent influence of only 'social' quantities of alcohol and a psychotropic drug could only be compelled to supply a specimen of breath or blood, but not both. Consequently, cases of alcohol-drug interaction went virtually unchallenged. To remedy this deficiency, an amendment to the 1968 legislation, passed in September 1974, required the suspected driver to provide a specimen of his breath and/or blood and/or urine for analysis. Thus, if a suspect's blood alcohol content is too low to be compatible with his behavior pattern, a medical examination is conducted to rule out other contingencies; and samples of the suspect's blood and urine are screened for evidence of drug usage. Findings are then presented before the court. Refusal to provide a specimen of breath and/or blood is deemed an expression of guilt, and attracts the same penalty as a conviction for driving under the influence of alcohol and/or a drug. A preliminary analysis of blood samples from Queensland drivers suspected of drug-alcohol affectedness from September 1974 to June 1976 suggests that the drug problem may be compared with the role of alcohol in traffic safety 30 years ago; and unless it is curbed, could parallel the present influence of alcohol on driving. Cautionary measures that can be taken by doctors and drug manufacturers are suggested for discouraging drug ingestion by drivers. Five references and three data tables are provided.